Screenings press



July 14, 1970 o. A. BUSSE ETAL SCREENINGS PRESS 2 bnuets-S'neet 1 Filed Dec. 8, 19d? INVENTOR. can 4w 4 51/555 //z/60 5. 44,6575

July 14, 1970 o. A. BussE ETAL SCREENINGS PRESS 2 Sheets-Sheet 2 Filed Dec. 8,, 1967 INVENTOR. 0577.40 4 51/5516.

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United States Patent 3,520,411 SCREENINGS PRESS Oswald Anton Busse and Hugo Erwin Klesper, Michelbach, Nassau, Germany, assignors to Passavant-Werke, Michelbach, Nassau, Germany, a corporation of Germany Filed Dec. 8, 1967, Ser. No. 689,197 Claims priority, application Germany, Dec. 9, 1966, 40 9 Int. Cl. B01d 37/04 US. Cl. 210-73 13 Claims ABSTRACT OF THE DISCLOSURE BACKGROUND OF THE INVENTION This invention relates to the field of separating solids from a liquid and, more particularly, to the waste-water treatment field in which it is desired to remove sewage sludge, fibers and other coarse material from a liquid so as to expedite subsequent treatment of both solids and liquid separately. Prior apparatus to perform the process of separating solids from a liquid by compression often were troubled with one of two common problems, or both. In order to deliquify the mixture substance to the desired degree, prior devices either compressed the substance for a long period of time to achieve a desired dryness and consequently had a small flow rate of solids discharge, or the compression operation was maintained for a relatively short period of time which allowed an increased flow rate of the solids discharge, but it was not effectively deliquified. With either disadvantage, the total performance is unsatisfactory because of the lack of quality or quantity of the solids produced. It is very desirable, in the wastewater treatment industry, to produce relatively dry solids because incineration is sometimes used to reduce the volume of solids produced. This reduces the amount of space and equipment necessary to store and dispose of the solids by another method, a factor which can be important in large metropolitan areas.

SUMMARY OF THE INVENTION The disadvantages and inefficiencies of prior apparatus and methods for separating solids from a liquid have been obviated by this invention. This invention allows the handling of a high volume of mixture and the eificient separation of the solids from the liquid to form a uniform, relatively dry solids product. This is accomplished by subjecting each portion of incoming mixture to a series of different compressive loads while transmitting the portion through a series of corresponding chambers provided with openings designed to facilitate the removal of liquid while simultaneously restraining the solids, all according to the combined factors of solids consistency, openings. size and the compressive load within each chamber. Depending upon the consistency of the portion of mixture to be processed, the degree of compressive load required varies as does the amount of restraint required to retain the solids while extracting the liquid. Therefore, instead of subjecting the entire portion of substance to a compressive load for a fixed period of time without varying the degree of restraint on the solids, each of the factors governing efficient separation of solids from the ice liquid (compressive load, time and degree of restraint) are varied according to the consistency of the substance. In this manner, free liquid in a fresh portion of mixture can be removed rather quickly under low compressive load and a small degree of restraint, while entrained and absorbed liquid can be extracted by subjecting the mixture to a higher pressure for a longer time.

The compressive force is supplied by a piston which travels through a series of aligned cylindrical chambers, each of which has a plurality of openings of a different size and shape to allow the expulsion of liquid while retaining the solids. Resistance to the axial movement of the piston is provided by accumulated solids compacted in the last chamber which is aided by a curved discharge chute having a gate mounted within. The incoming substance is pressure loaded in the first of the successive chambers to lessen the time required to separate free, or nearly free, liquid. The piston then travels through the first chamber to intercept and isolate a portion of mixture to compress it, remove free liquid to increase the proportion of solids within the portion and drive the portion into the next chamber where the pressure is increased, as is the degree of restraint, so that further deliquification can be achieved while preventing the solids from being removed with the liquid. While the portion of mixture substance is now substantially deliquified, the piston continues to drive it into the last chamber where it is compacted against previously deliquified portions still under pressure to prevent reunification with liquid. The piston continues to push the deliquified solids portion through the final chamber to an extent that an equal value of solids is displaced from the end of the chamber and discharged for disposal by one of any several means such as incineration or use as land fill.

A hydraulic control system is connected to the piston and gate to coordinate the compression and discharge processes.

The method and apparatus for this invention can, therefore, allow rapid operation of each compression cycle while maintaining high quality of the dryness of the solids produced and the proportion of solids removed from the liquid.

It is, therefore, an object of this invention to provide apparatus to efficiently and rapidly separate solids from a mixture of solids and liquid and to discharge the solids in a consistency suitable for incineration.

It is another object of this invention to provide apparatus for separating solids from a liquid by means of applying variable degrees of compression in connection with corresponding variable degrees of time and restraint of the solids.

A feature of the invention is the provision of a plurality of deliquification chambers each of which is designed to facilitate the removal of liquid from a mixture of solids and liquid in the shortest period of time depending on the consistency of the solids contained in the portion of liquid as it travels through each chamber.

Another feature of this invention is the provision of a gate and discharge chute which allows removal of compact solids from the apparatus while providing sufficient back pressure to simultaneously compact newly formed solids.

Still another feature of the invention is the use of adjustable pressure during the compaction process which allows lower operating costs while producing high quality compacted solids at a high rate.

Other objects, features and advantages of this invention will become readily apparent to those skilled in the art when the description of the preferred embodiment is read in conjunction with the drawings which are made a part hereof.

BRIEF DESCRIPTION OF THE DRAWINGS DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 shows the entire press apparatus in section and it should probably be studied in connection with FIG. 6 to obtain a full understanding of its operation. A frame '1 encloses several cylindrical chambers 2, 3 and 4 which are aligned axially end to end. Inlet chamber 2 contains an inlet feed opening 2A at its top to allow the entry, under pressure, of a portion of mixture substance which is mostly in liquid form and contains solids which are desired to be removed. Whenthe press is in its normal operating position, all of. the chambers 2, 3 and 4 have their principal longitudinal axes (axis of revolution) in the horizontal plane. In this position, the top side of inlet chamber 2 is open to receive a portion of mixture through opening 2A. Both ends of chamber 2 are also open, with the right end (the first end) being filled with the end of piston 6. A plurality of holes are located through the lower half of the wall of chamber 2 so that liquid can readily be drained through and be channeled out of the press through outlet 5. Since the solids content of the incoming portion of mixture may be relatively low in some instances, a relatively high percentage of the liquid may be in the form of free water in the case where the mixture is waste water in a sewage treatment plant. Free water might be defined for this purpose as being the water and very small impurities contained therein which can be either skimmed away from the solids, removed by filtering through a coarse filter, or removed under relatively low pressures such as 50 p.s.i.g. or below. Entrained or absorbed water, as opposed to free water, is that water which would not readily filter out, or run out, of a mixture of water and solids without pressure being applied.

Inlet chamber 2 is designed to remove liquid comprising free water and small impurities quickly since little pressure is required to separate this liquid from the large solids deposits. Within the inner bore of inlet chamber 2, running parallel to its longitudinal axis, is a plurality of axially extending grooves or recesses 16, each of which communicates with some of the holes 17 which are located in the lower half of the chamber. These recesses 16 allow the free Water to collect for discharge into outlet 5 with a minimum of back pressure. Recesses 16 are clearly shown in section in FIG. 5.

To the left of inlet chamber 2, within frame 1, as shown in FIG. 1, is compression chamber 3. The second end of inlet chamber 2 abuts the first end of compression cham; ber 3. FIG. 4 shows a cross section of compression chamber 3 throughsection B-B. Compression chamber 3 is mounted so as to provide a concentric space 50 between its outer perimeter and the inside of frame 1, said space 50 communicating with outlet 5. The inner bore of compression chamber 3 is cylindrical andhas a diameter substantially equal to that of inlet chamber 2. A plurality of slots 19 extend radially outwardly, as shown in FIG. 4, from the center of chamber 3 and extend axially substantially the entire length of the chamber. Slots 19 are designed to allow liquid to be driven into space 50 when pressure, generally in the range of about 40 p.s.i.g. to about 250 p.s.i.g., is applied within chamber 3. Space 50 communicates with outlet 5 to discharge the liquid.

Slots 19 have a width, as measured circumferentially on the inner bore, of from 1 to 5 millimeters. This dimension increases uniformly as the slots extend radially outwardly through the. thickness of the wall of compression chamber 3.

Directly to the left of compression chamber 3 Within frame 1, as shown in FIG. 1, is solids chamber 4. The second end of compression chamber 3 abuts the first end of solids chamber 4. FIG. 3 shows a cross section of solids chamber 4 through section AA. Like compression chamber 3, solids chamber 4 has a space 51 between its outer periphery and the inside of frame '1. Space 51 also communicates with outlet 5 via space "50. Within solids chamber 4 are a plurality of slots 20 which have discharge end 12. A hydraulic cylinder 14 is mounted between frame '1 and gate 13 and is capable of moving gate 13 to a restricting position 13 by extending its piston 15.

To the right of inlet chamber 2, as shown in FIG. 1, a cylindrical piston 6 is mounted in frame 1.' Piston 6 is slidably mounted within frame 1 on guide bars 10 and'll which are parallel and support yoke 7 on the outer end of piston 6 which doesnt contact chamber 2. When piston 6 is in its extended position, as shown in FIG. 1, its inner face seals the right end of inlet chamber 2 since its diameter is substantially equal to the diameter of the inner bores of chambers 2, 3, 4. The longitudinal axes piston 6 and chambers 2, 3 and 4 are coincident and parallelto the longitudinal axes of guide bars 10 and 11.

In operation, a portion of mixture substance containing solids and liquid is introduced under pressure into inlet chamber 2. In the case where the mixture is waste water such as sewage, the solids may comprise fibers and sludge while the liquid is primarily water. The free water is encouraged to travel through holes 17,- 18 in the wall of inlet chamber 2 and'out and be discharged throughout outlet 5 under pressure of piston 6 which moves to the left to intercept and isolate a portion of mixture, drive out some water and transmit the remainder to the left into compression chamber 3. As shown in FIGS. 2 and 6, a pair of hydraulic pistons 8 and 9 are mounted on frame 1 and are linked to piston 6 through yoke 7. As explained in more detail hereafter, pistons 8 and 9 deliver pressure to piston 6 so that it imparts relatively low compressive load of up to about 50 p.s.i.g. to the mixture in chamber 2 to encourage rapid removal of water from the solids. Generally, 40 p.s.i.g. is sufficient. Since the incoming mixture may contain a relatively high proportion of free water, the time and pressure required of piston 6 to separate the solids are A not large and piston 6 can travel through chamber 2 quite rapidly and-still efficiently perform this phase of separating the solids from the free liquid.

To jump ahead a bit, before describing the operation within compression chamber 3, it should be understood that in steady state operation, solids chamber 4 is completelyfilled with compacted solids all the Way up against gate 13 which is in restricting position 13 to provide back pressure. Actually, the curved shape of discharge end 12 also provides some back pressure.

Piston 6 continues into compression chamber 3 and increases pressure up to a relatively high (about 250 p.s.i.g) level and forces the mixture portion containing solids and entrained and absorbed water against the tightly packed compressed solids in chamber 4. Generally, thehigh pressure does not exceed 200 p.s.i.g. The entrained water is forced out of slots 19, into space 50 and out discharge outlet 5. As piston 6 continues on into solids chamber 4, the

newly compacted portion of solids from compression chamber 3 is forced into solids chamber 4. Gate 13 is lowered into open position 13, as shown in FIG. 1, and the injection of freshly compressed solids portion from compression chamber 3 into the first end (the end adjacent compression chamber 3) of chamber 4 causes a nearly equal amount of compressed solids to be discharged through outlet 12.

Since the solids are primarily dehydrated in compression chamber 3, the pressure there is applied for a period of from 2 to about 30 seconds, depending on the solids consistency, to effectively dehydrate the solids to a substantially dry consistency. Ten seconds is a normal average period. This pressure-is also applied to the previously compacted solids portions in solids chamber 4 so that water can not be transmitted through the compacted solids to be discharged. When gate 13 is opened for discharge, the back pressure effective on solids chamber 4 is reduced and a lower pressure of up to 40 p.s.i.g. (generally about 30 p.s.i.g) is all that is required to discharge a portion of compacted solids. This allows a smaller, more economical pump to be used to activate hydraulic cylinders 8 and 9 during this part of the operation cycle. The first part of the operation cycle, in inlet chamber 2, also benefits from the use of a smaller pump.

FIG. 6 illustrates a hydraulic system comprising valves, switches, pressure cylinders and pumps which collectively can be referred to as a. control system. This control system is illustrative of a manner in which the operation of the press can be made more automatic.

In operation, low pressure pump 21, driven by electric motor 24, pumps a fluid 23 into hydraulic tubes 25 with valves 28, 29 and 31 in their left leftmost and rightmost positions, respectively. This pressurizes the faces of hydraulic pistons 32 and 33 to push piston 6 to the right, as shown in FIGS. 1 and 6, out of inlet chamber 2 and also closes gate 13 to its restricted position 13'. A fresh portion of waste water mixture is now introduced into inlet chamber 2 via inlet 2a- With mixture in inlet chamber 2 and gate 13 in its restricted position, valve 31' is moved to its leftmost position and valve 28 is moved to its rightward position to pressurize the rod ends 26, 27 of pistons 32, 33, respectively. Low pressure of about 40 p.s.i.g. pulls yoke 7 via rods 8, 9 to drive piston 6 into and through inlet chamber 2 to remove free water from the mixture and transmit the solids into compression chamber 3. i

As piston 6 enters compression chamber 3, high pressure pump 22 takes over as prime mover and a pressure of about 200 p.s.i.g. is exerted on the solids in chamber 3 for about 10 seconds to extract the entrained and absorbed water.

It should be now stated that when starting operation, piston 6 drives the solids into solids chamber 4 and against gate 13 several times to build up a layer of compacted solids in solids chamber 4 equal to about 3 to 5 times the amount of solids contained in each incoming portion in inlet chamber 2. Low pressure, about 30 p.s.i.g., is all that is required to transmit solids into solids chamber 4 in a relatively dry condition so that water will not re-enter. A pressure switch (not indicated) is therefore energized when piston 6 leaves compression chamber 3 and this moves valve 28, as shown in FIG. 6, to its leftmost position to relieve hydraulic pressure in lines 25, after which valve 28 is moved to its rightmost position and low pressure pump 21 is operated to move piston 6 into chamber 4. Valve 28 is then returned to its leftmost position and valve 31 is moved to its rightmost position to move piston 6 to the right, back out of chamber 2.

With each succeeding stroke of piston 6, after an accumulation has been built up on solids chamber 4, valve 29 is moved to its rightmost position so that gate 13 is allowed to open to its non-restricting position just as piston 6 enters chamber 4 with a fresh portion of solids. This allows relatively dry solids material to be deposited while simultaneously dry providing suflicient back pressure to prevent water from re-entering the solids remaining in solids chamber 4. The deposited solids may be incinerated directly if desired.

Not shown on the drawings are two stop switches mounted on the frame, one at each end thereof, and arranged to be contacted by piston 6 as it reaches a predetermined point into solids chamber 4 and out of inlet chamber 2 which are the extreme points of its reciprocating travel. These stop switches can be used to either manually operate valves 28, 29 and 31, or connected to them directly for more automatic operation.

Thus it is seen that a novel screenings press has been described which achieves the objects and advantages set forth. It will be appreciated that an especially effiient operation is provided wherein the initial dehydration stepwhere the water is easiest to removeis accomplished with low pressure in little time, the second compression stepwhere the water is the most diflicult to removetakes longer at higher pressure while the final compaction and removal step also is performed in little time at low pressure. Thus, all steps combine to produce the final product in the shortest time.

While one preferred embodiment has been shown and described, it is understood that changes and modifications can be made in the apparatus, particularly in the control system, without departing from the spirit and scope of the principles taught and the invention should not be limited to the specific form disclosed.

Having thus described the invention, what is claimed is:

1. Apparatus for removing solids from a mixture of solids and liquid, comprising in combination:

a frame having an inlet, a liquid outlet and a solids outlet;

an inlet chamber within the frame having first and second end, said inlet chamber being in communication with the inlet for receiving a quantity of said mixture therefrom and having a plurality of openings therein communicating with the liquid outlet;

a compression chamber within the frame having a plurality of openings therein communicating with said liquid outlet, and first and second ends with said first end adjacent the inlet chamber and in communication with said second end of said inlet chamber;

a solids chamber within the frame having a plurality of openings therein communicating with said liquid outlet, and first and second ends with said first end adjacent the compression chamber and in communication with said second end thereof, and said second end in communication with the solids outlet;

a piston slida'bly mounted on said frame adjacent the first end of said inlet chamber, and adapted to reciprocate through said inlet, compression and solids chambers successively;

first reversible fluid operated power means attached to said piston and adapted to drive said piston through said inlet, compression and solids chambers successively to force liquid through the openings while compacting the solids within the solids chambers and discharging a portion of solids from the outlet;

the said openings in the inlet chamber being larger than those in the compression chamber and the solids chamber such that a major portion of the free liquid in the mixture is removed at the said inlet chamber;

a fluid pump means for pressurizing fluid to operate the said first power means to reciprocate the piston, said pump means including means for developing both a relatively low pressure and a relatively high pressure, control means for causing the said relatively low pressure fluid to operate the piston as the piston travels through the inlet chamber and through the solids chamber, and means for causing the said relatively high pressure to operate the piston as it reciprocates through the compression chamber.

2. Apparatus as set forth in claim 1, wherein:

each of said inlet, compression and solids chambers has an inner bore of substantially the same cross sectional area in a plane perpendicular to the direction of piston travel, and each has a longitudinal axis which is mutually coincident.

3. Apparatus as set forth in claim 1, wherein:

said openings in the compression and solids chambers are slots which extend lengthwise in -a direction substantially parallel to the longitudinal axis, and are from about 1 to about 5 millimeters wide as measured on the inner bore.

4. Apparatus as set forth in claim 1, wherein:

a plurality of axially extending recesses are formed in the inner bore of the inlet chamber, each of said recesses communicating with some of the openings in said inlet chamber to facilitate liquid removal therefrom.

5. Apparatus as set forth in claim 1, wherein:

said outlet is curved whereby resistance to solids traveling along the longitudinal axis of the solids chamber is increased.

6. Apparatus as set forth in claim 1, further including:

a movable gate mounted on the frame in the solids outlet, said gate being adapted to allow solids to be expelled under pressure of the piston when in an open position and increasing back pressure within the solids chamber when in a restricting position.

7. Apparatus as set forth in claim 6, wherein:

the plane of the gate when restricting the outlet is substantially parallel with a plane containing the longitudinal axes of the inlet, compression and solids chambers;

second power means are mounted to said frame and gate to move said gate between the open and restricting positions.

8. Apparatus as set forth in claim 7, further including:

control means operatively connected to said first and second power means, said control means being adapted to synchronize the first and second power means such that the gate is moved to the restricted position while the inlet chamber is receiving fresh quantity of mixture and the piston is subsequently moved through the inlet, compression and solids chambers successively to (a) remove liquid from the substance, (b) leave a quantity of freshly deliquified solids near the first end of the solids chamber and, (c) simultaneously reopen the gate and force discharge of an approximately equal quantity of solids from the outlet;

first and second stop means mounted to said frame near the inlet and solids outlet ends, respectively, and connected with said control means to cooperate and continuously reverse the piston travel after it has travelled a predetermined distance into the solids and inlet chambers, respectively.

9. A method for removing solids from a mixture of solids and liquid comprising the steps:

(a) subjecting a portion of mixture to a relatively low pressure while restraining the solids, while concurrently removing free liquid therefrom:

(b) subjecting the mixture to a relatively high pressure while continuing to restrain the solids, thereby removing entrained liquid therefrom:

(0) again subjecting the mixture to a relatively low pressure while partially reducing the restraint on the solids, to remove a portion of said solids from said restraint without re-entry of liquid thereinto, and repeating said steps as a cycle to thereby accumulate a quantity of compacted solids, whereafter each succeeding cycle introduces an amount of additional compacted solids and an approximately equal amount of compacted solids is simultaneously withdrawn.

10. A method for removing solids and liquid from a mixture as set forth in claim 9, wherein:

said quantity accumulated is about 3 to 5 times greater than said amount of additional compacted solids introduced in each succeeding cycle.

11. A method for removing solids and liquid from a mixture as set forth in claim 9, wherein:

the first said low pressure is about 40 p.s.i.g.;

said high pressure is about 200 p.s.i.g.; and

the second said low pressure is about 30 psig 12. A method for removing solids and liquid from a mixture as set forth in claim 11, wherein:

said high pressure is applied for a period of up to 30 seconds.

13. A method for removing solids from a mixture of solids and liquids comprising the steps of;

(a) placing the mixture into the inlet chamber of an apparatus having said inlet chamber and also a compression chamber and a solids chamber, all chambers being aligned with, and in communication with each other;

(b) exerting a relatively low pressure on the mixture in the inlet chamber to concurrently remove the free water from the mixture and also move the remainder of the mixture to the compression chamber;

(0) restraining the mixture in the compression chamber and exerting a substantially higher pressure on the mixture in said compression chamber to remove entrained liquid from the mixture while concurrently moving the remainder of the mixture to the solids chamber, and

(d) removing a portion of the restraint from the mixture and exerting a relatively low pressure on the mixture in the solids chamber to remove at least a portion of the solids from the apparatus without re-entry of liquid thereinto.

References Cited UNITED STATES PATENTS 783,602 2/1905 Wheelwright 106 2,386,052 10/1945 Lundy. 2,817,288 12/1957 Peters 10052 3,276,994 10/ 1966 Andrews 210-73 X 3,389,795 6/1968 Wintzer 2l01l2 JOHN W. ADEE, Primary Examiner US. Cl. X.R. 

